The invention relates to an intake and fuel/air mixing system for multi-cylinder, externally ignited internal combustion engines with at least two inlet valves per cylinder, at least two separate intake pipe arms for the inlet valves per cylinder, and fuel injection into the intake system.
In internal combustion engines of this kind the two inlet valves of each cylinder are usually connected to a common intake pipe and an injection nozzle is assigned to each cylinder. Such a design is relatively simple to build, but its drawback is that a load and speed dependent control of the charge movement in the intake pipe arms and in the cylinder is not possible since in this design a partial flow of the charge fed into the cylinder cannot be throttled. In addition, when the air flow rates are low, the velocity of the flow of the fresh air (or mixture with recirculated exhaust gas--EGR) is low so that the mixing of fuel and air is inadequate. Due to the rapidly released, large opening cross sections in multi-valve engines, residual gas content is high during idle and with low partial load. In this state, in connection with the low charge movement in the combustion chamber, unstable combustion and low efficiency are unavoidable.
A control of the charge movement in the cylinder that is adapted to the air flow rate can be achieved with intake systems that exhibit two completely separate intake pipe arms per cylinder. If one of these arms closes partially or totally when the air flow rates are low, the charge movement and the turbulence in the combustion chamber are significantly increased and thus, the combustion process is improved. The consistent design of such an intake system with completely separate intake pipe arms up to the inlet valves would, however, require twice the number of injection nozzles as compared to the current conventional systems. This design represents the most complicated and expensive solution from a manufacturing point of view.